The field of the invention is automated semiconducted wafer processing systems, used for processing semiconductor wafers, hard disk media, semiconductor substrates, optical materials, and similar materials requiring very low levels of contamination, collectively referred to here as xe2x80x9cwafersxe2x80x9d.
Computers, televisions, telephones and other electronic products contain large numbers of essential electronic semiconductor devices. To produce electronic products, hundreds or thousands of semiconductor devices are manufactured in a very small space, using lithography techniques on semiconductor substrates, such as on silicon wafers. Due to the extremely small dimensions involved in manufacturing semiconductor devices, contaminants on the semiconductor substrate material, such as particles of dust, dirt, paint, metal, etc. lead to defects in the end products.
To exclude contaminants, semiconductor substrates are processed within clean rooms. Clean rooms are enclosed areas or rooms within a semiconductor manufacturing facility, designed to keep out contaminants. All air provided to a clean room is typically highly filtered to prevent airborne contaminants from entering into or circulating within the clean room. Special materials and equipment are needed to maintain contaminants within the clean room at adequately low levels. Consequently, construction and maintenance of clean rooms can be time consuming and costly. As a result, the semiconductor processing equipment installed within a clean room should preferably be compact, so that large numbers of semiconductor wafers can be processed within a smaller space, thereby reducing space requirements and costs. Accordingly, there is a need for smaller semiconductor processing equipment, to reduce clean room space requirements.
Existing automated semiconductor processing systems use robots to carry the semiconductor materials. These robots are designed to avoid creating particles which could contaminate the semiconductors. However, even with careful design, material selection, and robot operation, particles may still be created by these robots, via their moving parts. Accordingly, there is a need for improved techniques for processing semiconductor substrate materials with very low levels of contamination to maintain the level of defects at acceptable levels.
In a first aspect of the invention, an automated semiconductor processing system has an indexer bay or space and a process bay or space within an enclosure. The indexer bay is oriented perpendicularly to the process bay, to form a compact design requiring less floor space in a clean room.
In a second separate aspect of the invention, an indexer is provided in the indexer bay. The indexer preferably holds pallets for supporting semiconductor wafers contained within cassettes. Pallet movers in the indexer move the pallets and cassettes in sequence from an indexer loading position, through a plurality of intermediate storage positions, to an indexer unload position. The indexer allows the automated semiconductor processing system to run continuously, by moving and storing cassettes.
In a third separate aspect of the invention, the pallet movers include an x-axis and y-axis shift system, for moving pallets longitudinally and laterally around in the indexer. Preferably the y-axis shift system has a pair of toothed belts engaging a rack on the bottom of the pallets, to prevent inadvertent movement of the pallets relative to the belts.
In a fourth separate aspect of the invention, prisms on the pallets redirect light beams from sensor pairs, to detect the presence or absence of a cassette on a pallet, or wafers in a cassette.
In a fifth separate aspect of the invention, a process robot within an automated semiconductor processing system has a robot arm vertically moveable along a lift rail. The robot arm has a forearm segment extending between an elbow joint and a wrist joint. A wafer holder on the robot arm is laterally offset from the elbow and wrist joints. The robot arm is compact yet has an extended range of travel. The processing system therefore requires less space.
In a sixth and separate aspect of the invention, a moveable buffer shelf is positioned over the indexer, to increase productivity and versatility of the system.
In a seventh and separate aspect of the invention, a novel process module door is provided to better close and seal a process module chamber.
In a eighth and separate aspect of the invention, an indexer or work-in-progress space is positioned under a docking station and transfer station, to provide a compact processing system.
In a ninth aspect of the invention, two or more of the features described above are combined to provide an improved automated semiconductor processing system.
It is an object of the invention to provide an automated semiconductor processing system, better designed to keep semiconductor wafers free of contaminants. It is a further object of the invention to provide an automated semiconductor processing system that is versatile, yet compact, to reduce clean room space requirements.
Other objects, features and advantages will appear hereinafter. The various features described among the embodiments may of course be used individually or in differing combinations. The invention resides not only in the systems described, but also in the subcombinations and subsystems described.